U.S. Pat. No. 4,075,532 discloses an improved cool white fluorescent lamp utilizing a two-component phosphor combination. The yellow emitting phosphor is disclosed as being as calcium fluoroapatite and two blue phosphors are disclosed which are a europium-activated strontium chloroapatite and a europium-activated barium-magnesium aluminate. The calcium fluoroapatite phosphor has an emission at one particular point on the CIE diagram at a given level of manganese activator. Therefore, the potential blue components that can be utilized with this material are somewhat limited. In addition, the strontium chloroapatite activated with europium is a material which also emits at a specific point on the chromaticity diagram. Furthermore, the europium-activated strontium chloroapatite is not as efficient phosphor as some other phosphors.
It is believed, therefore, that a combination which enables the use of a more efficient and brighter blue emitting phosphor in combination with a new yellow emitting phosphor component would be an advancement in the art.